WillGCT

Hey everyone, just bought a 96 F150 with the 5.0 and it has a pretty bad exhaust leak from the passenger side manifold to downpipe flange (the studs are rotted out) and the check engine light is on with codes P0171 and P0174 indicating bank 1 and bank 2 too lean. Could the massive exhaust leak be the cause of my CEL? Engine seems to be running very smooth and I don't hear any obvious vacuum leaks.

SouthDakota95F150

It most certainly could cause the codes to pop up! If all of the exhaust isn't getting down to the sensor it'll give it a false reading and make it say its running lean. I would think your mileage would take a beating too since your computer will be dumping in more fuel to compensate for the "lean" condition.

WillGCT

Thanks. I was able to get the flange fixed and now the exhaust is much quieter. Found out I also have a small manifold leak on the passenger side, but I'm going to leave it alone for now as it's not bad at all. I'll clear the codes and see what happens.

SouthDakota95F150

Right on. Hope it does the trick

WillGCT

Unfortunately I must have another issue going on as well, as both codes popped up again. Any suggestions? One of my coworkers has a nice Blue Point code reader/scan tool that he will let me borrow and I'll see whats going on.

SouthDakota95F150

Hmmm. See what you can find on the scanner and tell us what happens. I'll try to help you from there

SouthDakota95F150

Your O2 sensor could be bad too but lets not assume and throw parts at the problem

WillGCT

My truck has an O2 sensor in each manifold and that's it. Replaced the battery last night which cleared the codes but they both popped up again today while going up a hill that required me to keep my foot into it to maintain 65 on the highway. Like I said, I'll get a scan tool on it and see what the O2 sensors are saying to the PCM. Right now I'm averaging around 12 mpg.

SouthDakota95F150

Ah, you're rocking the OBDII system. Forgot they changed to that in 96. The OBDII system should be able to give you quite a bit more info than an OBDI so I assume that'll give you a good sense of direction. 12 mpg seems to be a little low, my 95 with the 302 and 206,xxx gets around 15 on the highway and its a supercab 4x4 with 31's. Then again, I dont know much about your truck or your driving habits. Is that mileage calculation at 65 or just combined city/highway?

Chris_1

iTrader: (1)

The 96 has 3 o2 sensors - the 3rd one is down between the 2 cats.